This invention relates to a process and apparatus for predicting the likelihood of success of a bypass, particularly in infrainguinal arterial reconstructions for treating severe limb ischemia.
Infrainguinal arterial reconstructions are well-established modalities for treating severe limb ischemia. However, bypass failures occur in many cases, particularly after reconstructions to infrapopliteal vessels. Because of this, a reliable predictor of bypass graft failure has been sought over the last two decades as a means for excluding patients from attempts or repeated attempts at revascularization. Various preoperative criteria, including arteriographic evaluation of the runoff bed and hemodynamic and clinical assessment of the degree of ischemia, have proven to be unreliable prognostic indices of graft outcome. Furthermore, intraoperative measurement of femoropopliteal bypass graft flow rates and outflow tract resistance have proven to be inconsistent predictors of graft patency.
Previous attempts to predict failure by assessing outflow tract resistance have been unsuccessful because the early and late failure of infrainguinal bypass grafts may be due to many factors other than this parameter. One confusing factor with the early studies is that all were performed on femoropopliteal bypasses in which outflow tract resistance was only rarely high enough that it alone would cause a failure. No comparable information, however, was available for bypasses to infrapopliteal vessels.
It is generally believed by vascular surgeons that poor graft outflow with high outflow resistance is an important cause of early graft failure. However, the techniques available for measurement of outflow resistance were generally unsatisfactory and could not serve as a predictor of the graft failure. Moreover, because of the rarity of early failures in femoropopliteal bypasses, even with bypass insertions into isolated popliteal artery segments, the outflow resistance measurement was of no discriminate value in predicting early failure of this operation.